Is there a genetic strategy to control nitrification and N2O emissions from agricultural systems? - biological Nitrification Inhibition (BNI)

Nitrification, a step in nitrogen (N) cycle, results in gaseous N emissions and NO3- leaching. In most natural ecosystems, where nitrification is reduced to a minor flux, do not leak N. In contrast, modern agricultural systems are characterized by unrestricted rapid nitrification, resulting in the loss of nearly 70% of fertilizer N inputs. Recently we proposed that certain plant species suppress nitrification by releasing inhibitory compounds from roots, a phenomenon termed ‘biological nitrification inhibition’ (BNI). Using a recombinant luminous Nitrosomonas europaea assay to detect and quantify nitrification inhibitors released from roots (i.e., BNIactivity), several plant species including tropical pastures, cereals and legumes were surveyed for BNI capability. Several major crops including wheat lacked significant BNI capacity. Tropical forage grass – Brachiaria humidicola and cereal crop - sorghum, showed the highest BNI-capacity. Significant genotypic variability for BNI-compound release was detected in B. humidicola and several high-BNI genetic stocks are identified. Volga or mammoth wildrye (Leymus racemosus) a perennial member of the Triticeae and a wild relative of wheat showed high-BNI capacity, thus can potentially provide necessary genes for introducing BNI capacity into cultivated wheat. Once released from roots, BNI-compounds are functionally stable in suppressing soil nitrification. Field plots planted with B. humidicola suppressed nitrification and N2O emissions; in contrast, soybean, a species that lacked BNI-capacity, stimulated soil nitrification. Our quest in seeking genetic solutions to reduce nitrification and N2O emissions will result in the development of low-nitrifying, low-N2O emitting agricultural systems and contribute towards restraining climate change and global warming.